How to use PEGjs in Node.js

This time I will bring you how to use PEGjs in Node.js, what are the precautions when using PEGjs in Node.js, the following is a practical case, let’s go together take a look.

(1)Install pegjs

npm install pegjs

(2)grammer.pegjs

start
  = additive
additive
  = left:multiplicative "+" right:additive { return left + right; }
  / multiplicative
multiplicative
  = left:primary "*" right:multiplicative { return left * right; }
  / primary
primary
  = integer
  / "(" additive:additive ")" { return additive; }integer "integer"
  = digits:[0-9]+ { return parseInt(digits.join(""), 10); }

(3)main.js

var fs=require('fs');var PEG=require("pegjs");
fs.readFile('./grammer.pegjs','utf8',function(err,data){  var parser=PEG.buildParser(data);  var result=parser.parse('1+2*3');  
  console.log(result);    // 7});

Note:
If The pegjs command line tool is required, and pegjs needs to be installed both in the project and globally.

npm install pegjs -g
npm install pegjs
pegjs grammer.pegjs parser.js

can generate a parser, parser.js

var parser=require('./parser.js');
parser.parse('1+2*3');    // 7

I believe you have mastered the method after reading the case in this article, and there will be more exciting things. Please pay attention to php Chinese websiteOther related articles!

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